Summarize the Basics of Networking Fundamentals, Including Technologies, Devices and Protocols

Summarize the basics of networking fundamentals, including technologies, devices and protocols

Basics of configuring IP addressing and TCP/IP properties (DHCP, DNS)

IP addressing

IP addresses enable systems running any operating system on any platform to communicate by providing unique identifiers for the system itself and for the network on which it is located. An IP address is a 32-bit value that contains both a network identifier and a host identifier. The address is notated using four decimal numbers ranging from 0 to 255, separated by periods, as in 192.

168.1.44. This is known as dotted decimal notation.

IP addresses represent network interface adapters, of which there can be more than one in a computer. A router, for example, has interfaces to at least two networks, and must therefore have an IP address for each of those network interface adapters. Workstations typically have only a single LAN interface, but in some cases, they use a modem to connect to another network, such as the Internet.

When this is the case, the modem interface has its own separate IP address (usually assigned by the server at the other end of the connection) as well as that of the LAN connection. If other systems on the LAN access the Internet through that computer’s modem, that system is actually functioning as a router.

The core protocols that TCP/IP uses to provide communication between computers the Internet Protocol (IP), the Transmission Control Protocol (TCP), and the User Datagram Protocol (UDP) rely on several other services in order to perform their functions.

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Some of these services take the form of independent protocols, such as the Address Resolution Protocol (ARP), which runs on every TCP/IP computer and enables IP to discover the hardware address of a computer using a particular IP address. Other services, such as the Dynamic Host Configuration Protocol (DHCP) and the Domain Name System (DNS), are both protocols and applications that run on their own servers.

DHCP (Dynamic Host Configuration Protocol) the core function of DHCP is to assign IP addresses.

• Is a combination of a client, a server, and a protocol that can automatically configure the TCP/IP clients on computers all over the network.
• Is capable of leasing IP addresses from a common pool to client computers, reclaiming them when they are no longer in use and then returning them to the pool for reassignment.

DNS (Domain Name System) When the Internet outgrew the HOSTS file, it also outgrew the flat name space the file used. There were too many systems to assign them each a unique single name. To address these problems, the TCP/IP developers created the Domain Name System (DNS), which enables administrators to assign hierarchical names to the computers on a network and resolve them into IP addresses as needed.

• Enables users to identify computers on a network using friendly names instead of IP addresses. DNS servers resolve the names into the IP addresses that computers need to communicate using TCP/IP.
• The DNS name space is hierarchical; a computer’s DNS name consists of a host name followed by two or more domain names, separated by periods.
• DNS servers store information in the form of resource records, which contain name-to-address mappings and other information.

Bandwidth and latency

Bandwidth: In computer networking with digital signals, bandwidth is the capacity of a communication channel for carrying signals. The greater the bandwidth, the more data can be transferred in a given time. Bandwidth is sometimes referred to as throughput, and for digital communication, it is usually measured in bits per second (bps) or a multiple thereof (Kbps, Mbps, Gbps, and so on).

Latency: The delay that occurs when a packet or signal is transmitted
from one part of a network to another. A network with high latency can experience
unpredictable delays. These delays usually do not affect data transmission appreciably
since network protocols such as Internet Protocol (IP) are connectionless, but
they have a serious impact on transmissions such as streaming audio and video
because the human ear and eye can easily detect latency in these forms of transmission.

Protocols (TCP/IP, NETBIOS)

TCP/IP

Transmission Control Protocol, A connection based Internet protocol responsible for breaking data into packets, which the IP protocol sends over the network. IP is located at the TCP/IP Internet layer which corresponds to the network layer of the OSI Model. IP is responsible for routing packets by their IP address.

IP is a connectionless protocol. which means, IP does not establish a connection between source and destination before transmitting data, thus packet delivery is not guaranteed by IP. Instead, this must be provided by TCP. TCP is a connection based protocol and, is designed to guarantee delivery by monitoring the connection between source and destination before data is transmitted. TCP places packets in sequential order and requires acknowledgment from the receiving node that they arrived properly before any new data is sent.

NetBIOS

Enhanced User Interface was designed as a small, efficient protocol for use in department-sized LANs of 20-200 computers that do not need to be routed to other subnets. NetBEUI is used almost exclusively on small, non-routed networks. As an extension of NetBIOS, NetBEUI is not routable, therefore networks supporting NetBEUI must be connected with bridges, rather than routers, like NetBIOS, the NetBEUI interface must be adapted to routable protocols like TCP/IP for communication over WANs.

Full-duplex, half-duplex

When two computers communicate over a LAN, data typically travels in only one direction at a time, because the baseband network used for most LANs supports only a single signal. This is called half-duplex communication. By contrast, two systems that can communicate in both directions simultaneously are operating in full-duplex mode. The most common example of a full-duplex network is the telephone system. Both parties can speak simultaneously during a telephone call and each party can also hear the other at the same time. An example of a half-duplex communication system is a two-way radio like a CB radio, in which only one party can transmit at any one time, and each party must say “over” to signal that he or she has finished talking.

Basics of workgroups and domains

Peer to Peer

In a peer-to-peer network, also called a workgroup, computers directly communicate with each other and do not require a server to manage network resources. A peer-to-peer network is most appropriate when fewer than ten computers are located in the same general area. The computers in a workgroup are considered peers because they are all equal and share resources among each other. Each user decides which data on his or her computer will be shared with the network. By sharing common resources, users can print from a single printer, access information in shared folders, or work on a file.

With peer-to-peer networking, you can:

• Use one computer to secure your entire network and protect your Internet connection.
• Share one Internet connection with all of the computers on the network.
• Work on files stored on any computer on the network.
• Share printers with all of the computers on the network.

Server Based

In a network with more than 10 users a peer to peer network will probably not be adequate. Therefore most networks have dedicated servers, which are not used as clients or workstations. On a server based network, certain computers act as servers while others act as clients. A server is simply a computer (or more precisely, an application running on a computer) that provides a service to other computers. The most basic network functions are the sharing of files and the sharing of printers; the machines that do this are called file servers and print servers. There are many other types of servers as well: application servers, e-mail servers, Web servers, database servers, and so on. A client is a computer that avails itself of the services provided by servers.

Common ports: HTTP, FTP, POP, SMTP, TELNET, HTTPS

LAN / WAN

Local area network (LAN) is a computer network covering a small geographic area, like a home, office, or group of buildings. Each node or computer in the LAN has its own computing power but it can also access other devices on the LAN subject to the permissions it has been allowed. These could include data, processing power, and the ability to communicate with other users in the network.

The defining characteristics of LANs, in contrast to WANs (wide area networks), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.

Wide Area Network (WAN) A group of networked computers in a large geographical area. The best example of a WAN is the Internet. WANs are used to connect (LANs) and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations.

Hub, switch and router

HUB

A hub or concentrator is a device used to connect all of the computers on a star or ring network. A hub, is nothing more than a box with a series of cable connectors in it. Hubs are available in a variety of sizes, from four- and five-port devices designed for home and small business networks to large rack-mounted units with up to 24 ports or more. Installing a single hub is simply a matter of connecting it to a power source and plugging in cables connected to the network interface adapters in your computers. However, it’s important for a network technician to understand what goes on inside a hub.

Like network interface adapters, hubs are associated with specific data-link layer protocols. Ethernet hubs are the most common, because Ethernet is the most popular data-link layer protocol, but Token Ring MAUs are hubs too, and other protocols, such as the Fiber Distributed Data Interface (FDDI) also use hubs.

Ethernet Hubs: An Ethernet hub is also called a multiport repeater. A repeater is a device that amplifies a signal as it passes through it, to counteract the effects of attenuation. If, for example, you have a thin Ethernet network with a cable segment longer than the prescribed maximum of 185 meters, you can install a repeater at some point in the segment to strengthen the signals and increase the maximum segment length. This type of repeater only has two BNC connectors, and is rarely seen these days. The hubs used on UTP Ethernet networks are repeaters as well, but they can have many RJ45 ports instead of just two BNC connectors.

When data enters the hub through any of its ports, the hub amplifies the signal and transmits it out through all of the other ports. This enables a star network to have a shared medium, even though each computer has its own separate cable. The hub relays every packet transmitted by any computer on the network to all of the other computers, and also amplifies the signals. The maximum segment length for a UTP cable on an Ethernet network is 100 meters. A segment is defined as the distance between two communicating computers. However, because the hub also functions as a repeater, each of the cables connecting a computer to a hub port can be up to 100 meters long, allowing a segment length of up to 200 meters when one hub is inserted in the network.

SWITCH

Switches are a special type of hub that offers an additional layer of intelligence to basic, physical-layer repeater hubs. A switch must be able to read the MAC address of each frame it receives. This information allows switches to repeat incoming data frames only to the computer or computers to which a frame is addressed. This speeds up the network and reduces congestion.

Switches operate at both the physical layer and the data link layer of the OSI Model.

ROUTER

A router is a networking devices used to extend or segment networks by forwarding packets from one logical network to another. Routers are most often used in large internetworks that use the TCP/IP protocol suite and for connecting TCP/IP hosts and local area networks (LANs) to the Internet using dedicated leased lines.

Routers work at the network layer (layer 3) of the Open Systems Interconnection (OSI) reference model for networking to move packets between networks using their logical addresses (which, in the case of TCP/IP, are the IP addresses of destination hosts on the network). Because routers operate at a higher OSI level than bridges do, they have better packet-routing and filtering capabilities and greater processing power, which results in routers costing more than bridges.

Routers contain internal tables of information called routing tables that keep track of all known network addresses and possible paths throughout the internetwork, along with the cost of reaching each network. Routers route packets based on the available paths and their costs, thus taking advantage of redundant paths that can exist in a mesh topology network. Because routers use destination network addresses of packets, they work only if the configured network protocol is a routable protocol such as TCP/IP or IPX/SPX. This is different from bridges, which are protocol independent.

Static routers: These must have their routing tables configured manually with all network addresses and paths in the internetwork.

Dynamic routers: These automatically create their routing tables by listening to network traffic. You can use routers, to segment a large network, and to connect local area segments to a single network backbone that uses a different physical layer and data link layer standard. They can also be used to connect LAN’s to a WAN’s.

Identify Virtual Private Networks (VPN)

Nodes on a public network such as the Internet that communicate among themselves using encryption technology so that their messages are as safe from being intercepted and understood by unauthorized users as if the nodes were connected by private lines

Basics class identification

To accommodate different size networks, IP defines several address classes. Classes A, B, and C are used for host addressing, and the only difference between the classes is the length of the NET_ID subfield:

Class A – addresses are intended for very large networks and can address up to 16,777,216 (224) hosts per network. The first digit of a Class A addresses will be a number between 1 and 126, the network ID start bit is 0 and default subnet mask is 255.0.0.0

Class B – addresses are intended for moderate sized networks and can address up to 65,536 (216) hosts per network. The first digit of a Class B address will be a number between 128 and 191, the network ID start bit is 10 and the default subnet mask is 255. 255.0.0

Class C – intended for small networks and can address only up to 254 (28-2) hosts per network. The first digit of a Class C address will be a number between 192 and 223, the network ID start bit is 110 and their default subnet mask is 255. 255. 255.0